mocha-wrap

Fluent pluggable interface for easily wrapping `describe` and `it` blocks in Mocha tests
39
By Jordan Harband

Fluent pluggable interface for easily wrapping describe, context, and it blocks in Mocha tests.

Example

var wrap = require('mocha-wrap');
var expect = require('chai').expect;

var mockWindow = {
    location: {
        href: 'test/url'
    }
};
wrap().withGlobal('window', () => mockWindow).describe('mocked window', function () {
    it('is mocked', function () {
        expect(window).to.equal(mockWindow);
    });

    it('has the right URL', function () {
        expect(window.location.href).to.equal('test/url');
    });
});

var obj = { a: 1 };
wrap().withOverrides(() => obj, () => ({ a: 2, b: 3 })).describe('overridden object keys', function () {
    it('has "b"', function () {
        expect(obj.b).to.equal(3);
    });

    it('has overridden "a"', function () {
        expect(obj.a).to.equal(2);
    });
});

wrap().withOverride(() => obj, 'a', () => 4).skip().describe('this test is skipped', function () {
    it('also supports .only()!', function () {
        expect(true).to.equal(false); // skipped
    });
});

Plugins

A mocha-wrap plugin is a named function that returns a MochaWrapper instance or a descriptor object.

  • A plugin’s function name must begin with the string “with”.

  • Plugins can be globally registered, or .used ad-hoc.

  • .use requires a plugin function as its first argument; further arguments are passed through to the plugin.

  • .extend requires a non-empty description string, and a descriptor object which may contain a value that is a function, or an array of functions, whose keys correspond to any or all of the supported mocha methods.

  • Globally registered plugins, .use calls, and .extend calls can be chained, stored, and reused - each link in the chain creates a new instance of a MochaWrapper.

  • A descriptor object may contain any or all of these 5 keys:

  • a description string, for use in “describe” and/or “it” (this is required when returning an object)

  • beforeEach: a function, or array of functions, for use in a mocha beforeEach function

  • afterEach: a function, or array of functions, for use in a mocha afterEach function

  • before: a function, or array of functions, for use in a mocha before function

  • after: a function, or array of functions, for use in a mocha after function

The most common approach will be for a plugin function to return this.extend(description, descriptor).

A plugin function must have a name that starts with “with”, and will be invoked with a receiver (”this” value) of a MochaWrapper instance.

To register a plugin, call the register function on mocha-wrap with the plugin function. This should not be done in a reusable module.

module.exports = function withFoo(any, args, you, want) {
    return this.extend('with some foo stuff', {
        beforeEach: function () {
            // setup ran before each test
        },
        afterEach: [
            function () {
                // teardown ran after each test
            },
            function () {
                // more teardown
            }
        ],
        before: function () {
            // setup ran once before all tests
        },
        after: function () {
            // teardown ran once after all tests
        }
    });
};

Usage

var wrap = require('mocha-wrap');
wrap.register(require('mocha-wrap-with-foo'));

wrap().withFoo().describe…

skip/only

Although mocha has describe.skip, describe.only, context.skip, context.only, it.skip, and it.only, it is not possible to implement these in mocha-wrap without using ES5 property accessors. Since this project supports ES3, we decided to use .skip().describe etc rather than forfeit the ability to have skip/only.

Tests

Simply clone the repo, npm install, and run npm test